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Larvicidal activity of chimeric Bacillus thuringiensis protoxins.
K C Raymond1, T R John, L A Bulla
1Department of Molecular Biology, University of Wyoming, Laramie 82071-3944.
Molecular Microbiology
|November 1, 1990
Summary
Bacillus thuringiensis subspecies kurstaki (Btk) and berliner (Btb) produce different insecticidal toxins. The amino-terminal half of these protoxins determines their specific larvicidal activity against insects.
Area of Science:
- Microbiology
- Insect Toxicology
- Molecular Biology
Background:
- Bacillus thuringiensis subspecies kurstaki (Btk) and berliner (Btb) produce lepidopteran-specific larvicidal protoxins.
- These protoxins exhibit varying activities against the same insect species.
- Protoxin toxicity is localized to the amino-terminal half, with the carboxy-terminal half being non-essential.
Purpose of the Study:
- To investigate the role of different protoxin domains in larvicidal activity.
- To determine which part of the protoxin dictates specific insecticidal activity.
Main Methods:
- Generation of protoxin chimeras by combining amino-terminal and carboxy-terminal halves from Btk and Btb.
- Comparison of wild-type and chimeric protoxins in bioassays.
- Larvicidal activity testing against tobacco hornworm (Manduca sexta) larvae.
Main Results:
- Protoxins are 90% homologous, with key differences in the amino-terminal half.
- A 26-amino acid insertion is present in the Btk protoxin's carboxy-terminal half.
- Chimeric protoxin studies confirmed that the amino-terminal half dictates specific larvicidal activity.
Conclusions:
- The amino-terminal domain of Bacillus thuringiensis protoxins is the primary determinant of specific larvicidal activity.
- Understanding domain function is crucial for developing targeted insect control strategies.